At present, the fiber materials for garments are generally the mixed fibers of polyester fibers as the synthetic fiber and cotton fibers as the natural fiber, and such mixed fibers are given a great deal of weight on the fiber industry in respective fields. In printing the mixed fibers, since the printing method and conditions of synthetic fibers and natural fibers are different from each other, it is disadvantageous in that two dying steps should be practiced to make the procedures complicate and falls down the economics.
As one strategy to overcome such disadvantages, U.S. Pat. No. 4,969,951 discloses the inks applicable to the mixed fibers using the reactive disperse dyes having both the characters of reactive dyes and disperse dyes, and the inkjet printing method using said inks. However, in preparing said inks the inks colloidized by dispersing the reactive disperse dyes in water are used. In preparing the printing inks through dispersion of dyes, the key is to obtain the stable colloid. However, since it is very difficult to obtain the stable colloid, it should be needed to practice special dispersion procedures such as milling procedure.
General dispersion procedures are presented as follows:
To prepare inks, first, dyes and dispersants such as lignin sulfonic acid and naphthalene polymers are homo-mixed in the aqueous system, and then dispersed by means of bead mill or pressure mill, for example, the trade name Microfluidizer manufactured by Microfluidic Inc. in USA. Then, the colloids prepared through micronization are suitably blended. The average particle size of the colloids thus obtained is about 150 nm.
However, it is very difficult to obtain the uniform result from every operations of such dispersion procedure. If the operations to maintain the average particle size below a certain level and to accurately set every property are not properly accomplished, the particles having a larger average particle size fill up the nozzles of inkjet head to cause a poor quality of the products, which makes the successive printing impossible. To the contrary, if the dispersion is too excessive, the particles having a small particle size are excessively increased to cause a change of properties of inks, which induces a change of discharge stability at inkjet head. Further, in order to maintain ultrafine particles much mechanical and electrical energy should be inputted.
Such fine particles are difficult to have the stability, have the storage stability only of six (6) months, and are further difficult to ensure the thermal stability. The reason why the dispersion procedure is practiced in spite of such complicated procedures is that the viscosity of inks should be extremely low in order to increase the color density in view of the characters of inkjet head. In case of the prior disperse dyes, the amount of dyes should be increased in order to increase the color density, and thus, the viscosity of dyes is increased. To prevent such increase in the viscosity the dyes should be present in the form of colloid so that the viscosity is not increased, and thus, can be converted into the inks.